Process for the purification of crystals containing foreign materials of a different specific gravity therefrom



A. BACKHAUS. PROCESS FOR THE PURIFICATION OF CRYSTALS CONTAINING FOREIGN MATERI ALS OF A DIFFERENT SPECIFIC GRAVITY THEREFROM.

Patented Nov. 15, 1921.,

APPLICATION FILED .IUNE 24,1918. 1,89%121.

2 SHEETSSHEE'I I.

A. A. BACKHAUS. PROCESS FOR THE PURIFICATION OF'URYSTALS CONTAINING FOREIGN MATERIALS OF A DIFFERENT SPECIFIC GRAVITY THEREFROM.

APPLICATION FILED JUNE 24,1918.

Patented Nov. 15, 19210 2 SHEETS-SHEET 2.

STATES ,PATET orno.

ARTHUR A. BAGKHAUS, F BALTIMORE, MARYLAND, ASSIGNOR TO U. S. INDUSTRIAL ALCOHOL 00., A CORPORATION OF WEST VIRGINIA.

PROCESS FOR THE PURIFICATION OF CRYSTALS CONTAINING FOREIGN MATERIALS OF A DIFFERENT SPECIFIC GRAVITY THEREFROM.

mower.

To all whom it may concern Be it known that I, ARTHUR A. BAoKHAUs, of Baltimore, in the State of Maryland, have invented a certain new and useful Improvement in Processes for the Purification of Crystals Containin Foreign Materials of a Different Specific ravity Therefrom, and

'. do. hereby declare that the following is a full, clear, and exact description thereof.

My invention relates particularly to a process for purifying crystals associated with admixed foreign materials having a different specific gravity than the specific gravity of said crystals, and relates especially to a process for separating crystals from organic coloring materials mixed therewith, as for example in the purification of oxalic acid.

The object of my invention is to provide i a process by means of which crystals may be readily separated from admixed foreign materials having a different specific gravity from said crystals, and particularly to en able oxalic acid crystals to be readily and quickly separated from the organic coloring materials which are found mixed therewith in the crude oxalic acid crystals produced. by the treatment of distillery waste.

A further object is to provide a process by which such separation may be carried out continuously until a particular quantity of crystals has been substantially entirely freed from the organic coloring materials.

Further objects of my invention will a e-- pear from the detailed description thereof 1 contained hereinafter.

Whilemy-invention is capable of being carried out in many different ways and in connection with many difierent types of apv paratus, I have shown only one type of apparatus for use in connection therewith in the accompanying drawings, in which Figure 1 is a side elevation of an apparatus which may be used in connection with my invention; and

Fig. 2 is a plan View of the same. In the drawings I have shown an agitating tank 1, open at the top for receiving the crystals to be separated from, the admixed organic coloring materials, and which is provided with a stirrer 2, having a plurality of downwardly-directed arms 3 for agitating the crystals located in said tank. Said stirrer 2 has a vertical shaft 4, supported.

Specification of Letters Patent.

Patented Nov. 15, 1921.

Application filed June 24, 1918. Serial No. 241,653.

within a strap 5, attached to the top of the -1 has at its side an inlet opening 9 leading to a valved inlet pipe 10 as, best shown, on Fig. 2,'to supply the washing liquor, which may be a saturated solution of ,oxalic acid, to be fed into the same. Both of'the pipes 9 and 10 connect with a vertical pipe 11, which connects. with a horizontal pipe 12 having two valved branches 13 and 14, which discharge into the tops of two vats 15 and 16, respectively. -The vats 15 and 16 are provided to allow the organic coloring matter to settle out from the liquor. The settling vats 15 and 16 are, furthermore, provided, respectively, with valved draw-off pipes 17 and 18, which are located above the level at which the settling particles of organic coloring matter will accumulate. These pipes 17 and 18 lead, by means of a valved pipe, 19, to a pump 20. Furthermore, the lowermost portions of the settling tanks 15 and 16 are connected by valved pipes 21 and 22 to said pipe 19 which leads to the pump 20. A draw-off overflow pipe 23 is, furthermore. provided to conduct the overflow from the agitating tank 1 to the settling tanks 15 and 16 by means of valved branch pipes and 25. Said pipe 23 is provided also with a valved branch pipe 25'? leading into the tank 1 at a lower level todraw off the bulk of the liquid before removing the crystals from the tank 1.

At the bottom of the agitating tank 1, there is also an outlet opening 26, controlled by a hand valve 27, which discharges into a chute 28, located so as to direct the discharged crystals into a filter 29. On the pipe 12 there is a valved branch pipe 29 to discharge liquor received from the settling tanks 15 and 16 into said filter from the pump 20. Said filter 29 may be" supplied with any desired quantity of fresh washing liquor by means of a valved pipe 30. The liquor drawn off from the filter 29 is conveyed by a valved pipe 31 to the pump 24.). I

Steam to operate the pump 20 is supplied by a pipe 32, and the exhaust therefrom passes out by a pipe 33. Y

In carrying out my process, a quantity of the oxalic acid or other crystals containing organic coloring matter or, the like, is inhroduced into the agitating tank 1, together with a quantity of a washing liquor, as for example a saturated solution of oxalic acid in water, which latter may be continuously supplied to said tank 1 by means of the pipe 10 through the operation of the pump 20. The stirrer 2 is then operated by the motor 8, and, while the liquor is being agitated to the proper extent to permit some restratification, that is, to cause the light organic coloring particles to approach the upper portion of the body of liquor while the oxalic acid crystals remain near the bottom thereof, the upper portion of the body of liquor is continuously conveyed away by the pipe 23, together with the particles of organic coloring material carried thereby, and is discharged by one or the other of the pipes 24 and 25 into one or the other of the settling tanks and 16.

Itis intended that one of the settling tanks 15 and 16 shall contain a body of the liquor at rest,'s0 as to allow the organic coloring materials to settle out therefrom, while the other of said tanks is receiving a further body of the liquor from the agitating tank 1, and that, as soon as the settling is completed in the tank in which the settling is-taking place, the operations in said tanks will be reversed.

\Vhen the settling has been completed in a particular tank, the liquor is drawn off therefrom through one of the pipes 17 and 18 by the pump 20, and is pumped therefroip through the pipe 10 into the agitating tan 1.

\Vhen sediment in either of the tanks 15 i and 16 has accumulated to a sufiicient extent,

this may be removed by means of one of the pipes 21 and 22 and the pump and dis charged into the filter 29, so as to remove the coloring matter therefrom, or the same may be discharged from the apparatus without passing into the filter 29.. g

After the crystals in the tank 1 have been subjected to washing in this manner, until they are substantially free from the organic coloring matter or, the like, the bulk of the washing liquid is conveyed away by the pipe 25*, and the purified crystals will then be drawn off from the tank 1 by the chute 28,

which discharges the crystals into the filter 29.

Any desired quantity of fresh washing the pump 20, and can thence be discharged into the agitating tank 1 by means of the pipe 10.

In this way crystals,as for example of oxalic acid, may be obtained substantially entirely free from the organic coloring materials.

Other crystals may be separated in the same way from admixed foreign materials.

l/Vhile I have described my invention above in detail, I wish it to be understood that many changes may be made therein Without departing from the spirit of the invention I claim:

1. The method of purifying crystals containing admixed foreign materials of a density less than said crystals but greater than the density of water, comprising agitating the crystals in the presence of a substantially saturated solution of the crystal substance in order to keep suspended said impurities and removing the supernatant liquid containing the suspended impurities which separate from the crystals lying at the bottom of the liquid, allowing said impurities to settle out from the liquid, and

reusing the liquid to repeat the treatment on a new batch of crystals.

2. The method of purifying crystals of oxalic acid containing admixed foreign materials of a density less than said crystals but greater than the density of water, comprising agitating the crystals in the presence of a substantially saturated solution of .the crystal substance in order to keep suspended said impurities and removing the supernatant liquid containing thesuspended impurities which separate from the crystals lying at the bottom of the liquid, allowing said impurities to settle out from the liquid and reusing the liquid to repeat the treatment on a new batch of crystals.

In testimony that I claim the foregoing I have hereunto set my hand.

AR'rH R A. BACKHAUS. 

